Enhancing efficiencies of solar thermophotovoltaic cells by downconversion of high-energy photons

To better suit the bandgap of solar cell, we proposed a novel theoretical model of solar thermophotovoltaic system, which consists of a concentrator, a surface-textured absorber, an emitter, a photovoltaic cell, and a downconversion layer. Two configurations of rear and front down converters are proposed to enhance the performance of the solar thermophotovoltaic system. The corresponding expressions of particle and heat fluxes are derived. Based on balance equations of particle and energy, the temperatures of emitter and solar cell, and the voltages of down converter are determined. In addition, the influences of solar concentration ratio, geometrical factor, and refractive indexes of emitter and solar cell are considered. Moreover, the operating voltage of solar cell, the areas of emitter and solar cell, and the bandgap of solar cell are optimized at the maximum efficiency condition. The results show that the existence of down converter can efficiently enhance the performance of the solar thermophotovoltaic system, and the proposed configurations can provide theoretical guidance for efficient solar energy harvesting.